A leak test is typically performed on a part that is intended to hold a pressurized volume of gas therein, either under a positive pressure or a negative pressure, in order to test for a leak in the part. A known form of leak testing is a water immersion test where the part, while pressurized, is immersed into a body of water. The presence of bubbles in the water, or the ingress of water into the part, would indicate the presence of a leak in the part.
This type of leak test however requires that every part that is to be tested get wet as well as subsequently dried, thereby requiring a large amount of time and space, as well as increasing costs. Further, since the part is immersed, the part can corrode due to the water and harmful contaminants within the water can come into contact with the part.
An alternative to water immersion leak testing are bubble leak detection devices. In these devices, a bubble chamber is connected to the part to be tested and to a secondary volume. A source of pressure is used to pressurize the part and the secondary volume, and once pressurization is complete, the pressure source is disconnected. If there is a leak in the test part, bubbles will appear in the bubble chamber due to a resulting pressure difference between the test part and the secondary volume. Examples of such bubble leak detection devices include United States Statutory Invention Registration No. H1045 to Wilson, U.S. Pat. No. 4,419,883 to Gelston, II, and U.S. Pat. No. 4,453,399 to Thompson.
A problem with these conventional bubble leak detection devices is that a sudden large change in pressure between the test part and the secondary volume, which can be caused during disconnection of the secondary volume, can cause liquid in the bubble chamber to backflow into the flow passage and into the secondary volume and/or out of the device, due to the resulting large pressure difference between the test part and the other side of the bubble chamber. Backflow of the liquid can cause a delay in further testing as the liquid takes a period of time to flow back into the bubble chamber, so that the bubble chamber will not show a leak immediately during the next test.
Further examples of devices for detecting leaks include U.S. Pat. No. 3,813,922, U.S. Pat. No. 4,068,522, U.S. Pat. No. 4,077,427, and U.S. Pat. No. 4,114,426.
There is a continuing need however for an improved bubble leak detection apparatus and method that is simple to use and results in extremely accurate tests.